Method for producing a waveguide, circuit device and radar system

ABSTRACT

A method for producing a waveguide in a multilayer substrate involves producing at least one cutout corresponding to a lateral course of the waveguide in a surface of a first layer arrangement comprising one or a plurality of layers. A metallization is produced on surfaces of the cutout. A second layer arrangement comprising one or a plurality of layers is applied on the first layer arrangement. The second layer arrangement comprises, on a surface thereof, a metallization which, after the second layer arrangement has been applied on the first layer arrangement, is arranged above the cutout and together with the metallization on the surfaces of the cutout forms the waveguide.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No.102019200689.2 filed on Jan. 21, 2019, and to German Patent ApplicationNo. 102019200893.3 filed on Jan. 24, 2019, the contents of which areincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates to methods for producing a waveguide,circuit devices and radar systems comprising a waveguide, and tomethods, circuit devices and radar systems in which a waveguide isintegrated into a multilayer substrate.

BACKGROUND

In radio-frequency circuit arrangements, it is typically necessary totransfer radio-frequency signals between different circuit structures.By way of example, radar systems can comprise transmitting/receivingcircuits, local oscillator circuits and antennas, between whichradio-frequency signals are transferred. In this case, radio-frequencysignals can be in a frequency range of 50 to 100 GHz and higher.

The requirements in respect of recognizing and differentiating variousobjects are constantly increasing particularly in the case of radarsystems in the automotive sector. One influencing variable here is thesize of the antenna aperture, which is substantially determined by thenumber of different transmission and reception channels. Typical radarsystems can thus have a plurality of transmitting/receiving circuits,which are sometimes also referred to as transceivers, wherein a typicalradar system can comprise for example three transmission channels, TXchannels, and four reception channels, RX channels. In order to increasean object differentiability, however, ever more channels are desirable,for example eight transmission channels and sixteen reception channels.Each transmission channel and each reception channel is generallyassigned a corresponding transmitting antenna and a correspondingreceiving antenna. It may generally be desirable for all transceivers touse the same, as far as possible phase-synchronous, radio-frequencylocal oscillator signal in order to down-convert received radar signalsto the baseband.

In order to transfer or to distribute such radio-frequency signals (RFsignals) in a circuit device, expensive printed circuit boards have beenused hitherto, wherein microstrip lines are provided on a specificradio-frequency substrate, RF substrate, in order to minimize thelosses. However, such known solutions have problems with regard toconduction losses, crosstalk and manufacturing tolerances. Inparticular, expensive materials are required for producing such RFsubstrates, wherein the RF substrates have a low tolerance vis-à-visprocess fluctuations and vis-à-vis variations of the dielectric.

Overview

Therefore, solutions enabling RF signal transfer in circuit devices withimproved properties in particular with regard to conduction loss andcrosstalk would be desirable.

Examples of the present disclosure provide methods, circuit devices andradar systems comprising at least one waveguide in a multilayersubstrate, such that RF signals can be transferred by way of thewaveguide in the multilayer substrate.

Examples of the present disclosure provide a method for producing awaveguide in a multilayer substrate which involves producing at leastone cutout corresponding to a lateral course of the waveguide in asurface of a first layer arrangement comprising one or a plurality oflayers. A metallization is produced on surfaces of the cutout. A secondlayer arrangement comprising one or a plurality of layers is applied onthe first layer arrangement, wherein the second layer arrangementcomprises on a surface thereof a metallization which, after the secondlayer arrangement has been applied on the first layer arrangement, isarranged above the cutout and together with the metallization on thesurfaces of the cutout forms walls of the waveguide.

Examples of the present disclosure provide a circuit device, having thefollowing features: a multilayer substrate; at least one waveguideintegrated into the multilayer substrate; a first layer arrangementcomprising one or a plurality of layers, wherein the first layerarrangement comprises a cutout corresponding to a lateral course of thewaveguide in a surface thereof; a metallization on the surfaces of thecutout; a second layer arrangement, which comprises one or a pluralityof layers and is applied on the surface of the first layer arrangement,wherein a metallization on the second layer arrangement is arrangedabove the cutout and together with the metallization on the surfaces ofthe cutout forms the waveguide, wherein the metallization on the secondlayer arrangement leaves open predetermined lateral regions of thecutout in a vertical direction; and coupling elements for couplingsignals into and out of the waveguide at the regions of the cutout thatare left open in a vertical direction.

Examples of the present disclosure provide a radar system having thefollowing features: a multilayer substrate; at least one waveguideformed in the multilayer substrate; and a first semiconductor radartransmitting/receiving circuit and a second semiconductor radartransmitting/receiving circuit, wherein the first semiconductor radartransmitting/receiving circuit is coupled to the second semiconductorradar transmitting/receiving circuit by way of the waveguide, or whereinthe first semiconductor radar transmitting/receiving circuit and thesecond semiconductor radar transmitting/receiving circuit are coupled toa local oscillator circuit by way of a respective waveguide.

Examples of the present disclosure are based on the insight that theintegration of a waveguide into a multilayer substrate in the mannerdescribed makes it possible to transfer and to distributeradio-frequency signals in a circuit device comprising the multilayersubstrate, wherein firstly conduction losses and crosstalk can bereduced or minimized and secondly expensive RF substrates can beomitted. The integration of waveguides in multilayer substrates in themanner described makes it possible to integrate waveguides flexibly incircuit devices comprising a multilayer substrate, on and in which RFelements, for example in the form of semiconductor circuits, such ase.g. semiconductor chips, and/or antenna elements are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present disclosure are explained in greater detail belowwith reference to the accompanying drawings, in which:

FIGS. 1A-1F show schematic illustrations for an example of a method forproducing a waveguide in a multilayer substrate;

FIGS. 2A-2F show schematic illustrations for a further example of amethod for producing a waveguide in a multilayer substrate;

FIGS. 3 and 4 show schematic illustrations of layers of a multilayersubstrate which comprise waveguide structures;

FIGS. 5-8 show schematic illustrations of various examples of circuitdevices in which a waveguide is integrated into a multilayer substrate;and

FIG. 9 shows a circuit diagram of an example of a radar system.

DETAILED DESCRIPTION

Hereinafter, examples of the present disclosure are described in detailusing the accompanying drawings. It should be pointed out that identicalelements or elements having the same functionality may be provided withidentical or similar reference signs in the drawings, in which case arepeated description of such elements may be omitted. Therefore,descriptions for elements having identical or similar reference signsmay be mutually interchangeable.

In the following description, a plurality of details are set out inorder to yield a more thorough explanation of examples of the presentdisclosure. However, it is evident to those skilled in the art thatexamples of the present disclosure can be implemented without thesespecific details. In other cases, sufficiently known structures anddevices are shown in a schematic cross-sectional view or plan viewinstead of their details being shown, in order not to obscure thedescription of examples. Moreover, features of the various examplesdescribed hereafter can be combined with other features of otherexamples, unless a contrary indication is expressly given herein.

An example of a method for producing a waveguide in a multilayersubstrate will now be described with reference to FIGS. 1A to 1F.Firstly, a cutout 12 is produced in a surface of a first layerarrangement 10. The layer arrangement 10 can comprise one or a pluralityof layers, for example layers composed of a ceramic or dielectricmaterial. FIG. 1A schematically shows a plan view of the first layerarrangement 10 and FIG. 1B schematically shows a cross-sectional viewalong the line B-B in FIG. 1A. A direction perpendicular to the mainsurfaces of the layer arrangement shall be defined as a verticaldirection, and a direction parallel thereto shall be defined as alateral direction. In plan view, the cutout 12 corresponds to a lateralcourse of the waveguide to be produced. To put it another way, thewaveguide to be produced extends laterally in the first layerarrangement and the cutout produced corresponds to a lateral course ofthe waveguide from a first lateral section thereof to a second lateralsection thereof. The first lateral section can be a first lateral end ofthe waveguide and the second lateral section can be a second lateral endof the waveguide.

As is shown in FIG. 1C, a metallization 14 is produced on surfaces ofthe cutout. The metallization 14 can continuously cover all surfaces ofthe cutout. After the metallization 14 has been produced, a second layerarrangement 20 comprising a metallization 22 on a surface thereof isapplied on the first layer arrangement 10. The second layer arrangement20 can in turn comprise one or a plurality of layers, for exampleceramic or dielectric layers. After the second layer arrangement 20 hasbeen applied on the first layer arrangement 10, the metallization 22 ofthe second layer arrangement is arranged above the cutout 12 andtogether with the metallization 14 on the surfaces of the cutout 12forms the waveguide, as is shown in FIG. 1D. The metallization 22 canlikewise be continuous in the region of the waveguide formed, such thattogether with the metallization 14 a waveguide with a continuousmetallization in the entire inner surface region of the waveguide isformed.

In examples of the present disclosure, the metallization on the secondlayer arrangement may not cover regions of the cutout at predeterminedlateral regions thereof, such that signal coupling into and signalcoupling out of the waveguide can take place by way of these regions. Inother examples, the metallization on the second layer arrangement isremoved in regions of the cutout at predetermined lateral regionsthereof after the second layer arrangement has been applied. FIGS. 1A toIF show one such example. As is shown in FIG. 1E, the metallization 22is removed at predetermined lateral regions 24 and 26 of the cutout 12.The lateral regions 24, 26 can be lateral ends of the cutout 12 inexamples. In examples, the removal can be carried out through openings28, 30 in the second layer arrangement 20. In examples, the second layerarrangement 20 can have the openings 28, 30 when it is applied. In theexample shown, the openings 28, 30 in the second layer arrangement 20are produced at the predetermined lateral regions of the cutout afterthe second layer arrangement 20 has been applied on the first layerarrangement 10, in order to make it possible to remove the metallization22 in the regions 24, 26.

In examples of the disclosure, the openings in the second layerarrangement have been or are metallized and form an extension of thewaveguide through at least parts of the second layer arrangement.

In the example shown in FIGS. 1A to 1F, producing the openings 28 and 30through the second layer arrangement 20 is followed by formingmetallizations 32 and 34 on surfaces of the openings 28 and 30 in thesecond layer arrangement 20. The metallizations 32 and 34 constitute anextension of the waveguide through the second layer arrangement 20, in avertical direction in the example shown. The waveguide produced thuscomprises vertical sections formed by the metallizations 32 and 34 and alateral section formed by the metallizations 22 and 14.

In the example shown in FIGS. 1A to 1F, the cutout 12 does notcompletely penetrate through the first layer arrangement 10 in avertical direction with respect to a main surface of the first layerarrangement 10. The lateral section of the waveguide is thus formed bythe metallization 14 on the surface of the cutout 12 and themetallization 22 on the surface of the second layer arrangement 20. Inother example implementations, the cutout can completely penetratethrough the first layer arrangement in a direction perpendicular to amain surface of the first layer arrangement, e.g. in a verticaldirection. One such example will now be described with reference toFIGS. 2A to 2F, these figures in each case again showing differentmethod stages during production.

FIG. 2A once again shows a schematic plan view of the first layerarrangement 10, in which a cutout 36 corresponding to a lateral courseof the waveguide is formed. As can be discerned in FIG. 2B, the cutout36 completely penetrates through the first layer arrangement 10 in thisexample. In the example shown, the cutout 36 completely penetratesthrough the first layer arrangement 10 over the entire lateral course.In other examples, the first cutout can completely penetrate through thefirst layer arrangement 10 at least in sections along the lateralcourse.

As is shown in FIG. 2C, a metallization 14 is produced on surfaces ofthe cutout 36. Afterward, a second layer arrangement 20 having ametallization 22 is applied on a first main surface of the first layerarrangement 10. Furthermore, as shown in FIG. 2D, a third layerarrangement 40 having a metallization 42 is applied on a second mainsurface of the first layer arrangement 10. The third layer arrangement40 can comprise one or a plurality of layers, for example ceramic ordielectric layers. The second layer arrangement 20 and the third layerarrangement 40 are applied on opposite sides of the first layerarrangement 10, such that the metallization 22 is arranged on a firstside of the cutout 36 and the metallization 42 is arranged on a secondside of the cutout 36 opposite the first side. The metallizations 22 and42 together with the metallization 14 on surfaces of the cutout 36 thusform the waveguide.

As is shown in FIGS. 2E and 2F, afterward the metallization 22 can onceagain be removed at predetermined regions 24 and 26, which can onceagain be carried out by way of openings 28 and 30 in the second layerarrangement 20. The openings 28 and 30 in the second layer arrangement20 can then once again be metallized in order to produce metallizations32 and 34 constituting an extension of the waveguide through the secondlayer arrangement 20.

In examples, waveguides are thus produced in a multilayer substrate byvirtue of metallizations being provided on various layer arrangementsand the layer arrangements being connected to one another in such a waythat the metallizations define walls of the waveguide. Waveguides havingvarious courses can thus be integrated into a multilayer substrate in aflexible manner. The multilayer substrate can be for example a substratewhich is additionally configured for receiving semiconductor componentsat regions provided therefor. Accordingly, the multilayer substrate cancomprise e.g. contact connection regions and electric lines, as knownfor instance from printed circuit boards for semiconductor components.

In examples, the metallization on the surfaces of the cutout and themetallization on the second layer arrangement and, if present, the thirdlayer arrangement extend continuously between the predetermined lateralregions. It is thus possible to form a waveguide having continuousmetallic surfaces, which waveguide enables low conduction losses and lowcrosstalk, in a multilayer substrate.

In examples of the present disclosure, provision can be made of couplingelements for coupling signals into and out of the waveguide at thepredetermined lateral regions at which the metallization on the secondlayer arrangement does not cover the cutout. Coupling elements 50 and 52are schematically illustrated by dashed lines in FIGS. 1F and 2F. Thecoupling elements can be formed for example by patch antennas designedto couple electromagnetic RF signals into the waveguide and/or to coupleelectromagnetic RF signals out of the waveguide.

In examples of the present disclosure, therefore, at least one couplingelement can be formed by an antenna, wherein the antenna can be formedin or on a housing of an RF circuit chip fitted in or on the multilayersubstrate, or wherein the antenna can be fitted on the multilayersubstrate. In examples, furthermore, reflectors can be provided on aside of the coupling elements facing away from the first layerarrangement.

In examples, the cutout can be formed in the first substrate arrangementby any suitable methods, for example by milling, by a laser treatment,by etching methods or the like. In examples, the first layer arrangementcan comprise a plurality of layers of the multilayer substrate, in whichlayers signal routing structures comprising vias and conductor tracksare formed. In examples, the second layer arrangement can comprise aplurality of layers of the multilayer substrate, in which layers signalrouting structures comprising vias and conductor tracks are formed. Inexamples, the first and second layer arrangements are fitted on aplurality of layers of the multilayer substrate, in which layers signalrouting structures comprising vias and conductor tracks are formed.

Examples of the present disclosure provide methods for producing acircuit comprising a multilayer substrate. The multilayer substrate isproduced comprising a plurality of layers, in which signal routingstructures comprising vias and conductor tracks are formed. Themultilayer substrate comprises RF elements on or in the multilayersubstrate. The RF elements can comprise transmitting/receiving circuitsand local oscillator circuits, for example. The RF elements can beformed by semiconductor circuits in the form of semiconductor chips. Atleast one waveguide is formed in the multilayer substrate by methods asdescribed herein, wherein at least one terminal of a first RF element iscoupled by way of the at least one waveguide to a terminal of a secondRF element for signal transfer between same.

In examples, the RF elements can comprise a local oscillator circuit, atleast one transmitting/receiving circuit and at least one antenna,wherein producing at least one waveguide comprises producing a waveguidethat couples the local oscillator circuit to the at least onetransmitting/receiving circuit, and/or producing a waveguide thatcouples the at least one transmitting/receiving circuit to the at leastone antenna. In examples, the circuit can be a radar circuit, whereinthe RF elements comprise a plurality of transmitting/receiving circuits,a plurality of receiving antennas, a plurality of transmitting antennas,and a local oscillator circuit, wherein producing at least one waveguidecomprises producing a plurality of waveguides in order to couple thelocal oscillator circuit to each of the transmitting/receiving circuits,and to couple the transmitting/receiving circuits to the plurality ofreceiving antennas and transmitting antennas.

Examples of the present disclosure are described below on the basis of aradar circuit device. However, there is no need to mention separatelythat other circuit devices in which RF signals are transferred can alsobe implemented using methods and devices such as are described herein.Generally, examples of the present disclosure are applicable to circuitdevices in which RF signals are transferred between RF elements, inparticular RF semiconductor circuits, e.g. semiconductor chips.

As was mentioned in the introduction, the requirements made of radarsystems in the automotive sector with regard to recognizing anddifferentiating various objects are constantly increasing, wherein, inorder to attain a desired number of channels, by way of example, aplurality of radar transceivers in a cascade circuit can be used. In thecase of such a cascade circuit, it is desirable for all transceivers touse the same, as far as possible phase-synchronous, radio-frequencylocal oscillator signal, LO signal, to down-convert the received radarsignals to the baseband. In examples, the radio-frequency localoscillator signal can have a frequency of more than 50 GHz, for examplebetween 76 and 81 GHz. The distribution of signals of such highfrequency entails a number of problems. Firstly, signals of such highfrequency are subject to specific losses on the printed circuit board,which has the effect that the power of the radio-frequency signals becorrespondingly high, which results in unnecessary heating of thecircuit that provides the radio-frequency signal. The circuit thatprovides the radio-frequency signal can be e.g. an LO master. The highpower consumption of the LO master can be a burden on the thermal budgetof the entire radar circuit and thus restrict the performance thereofand/or require expensive, complex measures for removing the heat.Furthermore, undesired crosstalk between the radio-frequency LO signaland the transmission and/or reception paths of the radar transceivers onthe printed circuit board can reduce the performance of the radarcircuit, which is sometimes also referred to as a radar sensor.Furthermore, expensive printed circuit boards have been requiredhitherto, wherein the properties of the printed circuit board materials,for example the dielectric conductivity and the coefficient of thermalexpansion, have been permitted to fluctuate very little, in order tokeep the influences, for example the signal damping, on the various LOpaths as constant as possible.

Besides the distribution of the radio-frequency LO signal, feed linesfrom the transceivers to the transmitting-receiving antennas are alsoaffected by the problems mentioned. Here, too, it is beneficial to keeplosses low and crosstalk low. Examples of the present disclosure serveto alleviate the problems mentioned using the integration of waveguidesintegrated into a multilayer substrate.

FIG. 9 schematically shows a circuit diagram of a radar circuitcomprising an LO circuit 60 and four transceiver circuits 62, 64, 66 and68. The circuits can be formed in each case by integrated circuits, IC,or integrated circuit chips. The LO circuit 60 constitutes an LO master,which makes a radio-frequency LO signal available to the transceivercircuits 62 to 68. The transceiver circuits 62 to 68 thus constitute LOslaves. In order to distribute the LO signal, the LO circuit 60 isconnected to the transceiver circuits 62 to 68 by way of an LOdistribution network 70. To put it more precisely, a respectivetransmission output TX1, TX2, TX3 and TX4 is connected to a localoscillator input LO_IN of a respective transceiver circuit 62, 64, 66,68 by way of an assigned signal line 72, 74, 76, 78. Each of thetransceiver circuits 62 to 68 has a plurality of transmission outputsand a plurality of reception inputs. In the example shown, eachtransceiver circuit 62 to 68 has two transmission outputs TX1, TX2 andfour reception inputs RX1, RX2, RX3 and RX4. The transmission outputsand reception inputs of the transceiver circuits are connected toreceiving antennas 82 and transmitting antennas 84 by way of RF signalfeed lines 80. The receiving antennas 82 and the transmitting antennas84 can be formed by patch antennas, as is shown in FIG. 9. FIG. 9 thusshows a typical LO distribution network and RF signal feed lines to theantennas for a radar frontend circuit having eight transmission channelsand sixteen reception channels. It goes without saying that comparablecircuits can also be implemented with a different number of channels.Furthermore, passive RF elements such as e.g. ring coupler structureshaving a plurality of inputs/outputs can also be formed by the waveguidehaving a corresponding shape and routing. In the case of cascaded radardevices, such ring coupler structures can make it possible that, in theevent of failure of a transceiver circuit operating as master, whichtransceiver circuit, in the original configuration, distributes the LOsignal to the radar devices operating as slaves, in a new configuration,a transceiver circuit operating hitherto as a slave becomes the newmaster, which undertakes the LO distribution to the further MMIC,without the need for an active switchover in the LO distributionnetwork. Likewise, in the present examples, the lateral course of thewaveguide can be configured arbitrarily and have for example straightsubsections, round subsections or angular subsections.

In examples of the present disclosure, one or more of the signal lines72, 74, 76, 78 and one or more of the RF signal feed lines 80 to theantennas can be implemented by a waveguide as described herein. Inexamples, a corresponding waveguide can be implemented for each RFsignal path of the radar circuit, e.g. both for all signal lines 72, 74,76 and 78 and for all RF signal feed lines 80 to the receiving antennas82 and the transmitting antennas 84.

In this case, a waveguide should be understood herein to mean awaveguide which is not filled with a solid material, e.g. which ismaterial-free. To put it more precisely, the interior between the wallsof the waveguide is not filled with a solid material, but rather with afluid, such as e.g. air. In this case, the dimensions of the waveguidecan be adapted to the desired frequency range. By way of example, Table1 shows typical dimensions and frequency ranges of waveguides having arectangular cross section.

TABLE 1 Recommended Waveguide frequency range Dimension A Dimension Bdesignation [GHz] [mm] [mm] WR12 60-90 3.0988 1.5494 WR10  75-110 2.541.27 WR8  90-140 2.032 1.016 WR6 110-170 1.651 0.8255 WR5 140-220 1.29540.6477

In Table 1, the first column shows generally used designations ofwaveguides. The dimensions A and B represent the inner side lengths ofthe rectangular waveguide. Table 1 reveals that the dimensions of thewaveguide decrease as the frequency increases. Examples of the presentdisclosure are thus suitable in particular for circuit devices, forexample radar circuits, for high frequency ranges of 60 to 220 GHz, forexample.

As has been explained above, in the case of a circuit arrangement asshown in FIG. 9, for example, all the RF signal lines can be implementedby waveguides. In this case, the arrangement of the elements of thecircuit diagram shown in FIG. 9 can be regarded as a layout whichadvantageously enables a corresponding connection of a local oscillatorcircuit 60 to transceiver circuits 62, 64, 66 and 68 and of thetransceiver circuits 62 to 68 to respective antennas 82 and 84. In orderto implement the signal connections, it is possible to use for examplewaveguides having a layout as shown in FIG. 3. In this case, FIG. 3shows a plan view of a first layer arrangement, and cutouts, only two ofwhich are designated by the reference signs 12 by way of example, havebeen produced in the first layer arrangement, as has been describedabove. As is shown schematically in FIG. 4, the first layer arrangement10 can comprise a plurality of layers 10 a to 10 d, in whichcorresponding cutouts for waveguides are formed. To put it moreprecisely, in plan view respectively overlapping cutouts in the variouslayers 10 a to 10 d jointly form a waveguide. It should be noted herethat FIG. 4 represents an exploded illustration and the layers 10 a to10 d are connected to one another at main surfaces thereof. In thiscase, the cutouts in the individual layers are generally produced afterthe layers have been connected. Consequently, by way of example, thecutouts 12 a, 12 b, 12 c and 12 d overlap in plan view and form acontinuous cutout, the lateral course of which corresponds to thelateral course of the waveguide that is integrated into a multilayersubstrate in accordance with the present disclosure. Furthermore, in oneexample of a layer arrangement 10, it may be possible to form respectivewaveguides in different layers, which can avoid crossing of waveguidese.g. in specific layouts.

In examples, the individual layers are firstly pressed in order toproduce the first layer arrangement 10, wherein cutouts are thenproduced in the correspondingly pressed layers, the cutoutscorresponding to the lateral course of the waveguide structures to beproduced. In examples, this cutout can have a U-shape in a verticalsection. In examples, the cutout can be produced by laser treatment orbe milled. The milled-out U-shape is then metallized and an upper layer,which constitutes a second layer arrangement in accordance with thepresent disclosure and has a metallization, is applied on the side inwhich the cutout is formed. The upper layer is then pressed with theother layers, such that the metallization on the upper layer and themetallization on the surfaces of the cutout give rise to the waveguide.

Examples of the present disclosure provide circuit devices which can beproduced using methods as described herein. To put it more precisely,each waveguide as described herein can be produced using individual orall method features as described herein.

Examples of such circuit devices in which a first RF circuit isconnected to a second RF circuit by way of a corresponding waveguidewill now be explained in greater detail with reference to FIGS. 5 to 8.It is assumed in this description that the first RF circuit is an LOmaster, e.g. a circuit that provides an LO signal, and the secondcircuit is an LO slave, e.g. a circuit that receives an LO signal.However, there is no need to mention separately that the first andsecond RF circuits can also be formed by other RF circuits.

As is shown in FIGS. 5 to 8, the circuit devices each comprise amultilayer substrate 100, into which a waveguide 102 is integrated. Thewaveguide here may have been produced in each case by a method asdescribed herein, wherein in such a case a possible boundary between afirst layer arrangement and a second layer arrangement is indicated by adashed line 104 in FIGS. 5 to 8.

In the example shown in FIG. 5, an LO master 110 and an LO slave 112,for example each in the form of an MMIC (monolithic microwave integratedcircuit) are provided on the top side of the multilayer substrate 100.In examples, the LO master 110 and the LO slave 112 can comprise an eWLBhousing (eWLB=embedded wafer level ball grid array). Vias 114 and signallayers 116 can be provided in the multilayer substrate 100. Theseconstitute other signal routing structures 118 in the multilayersubstrate. In the example shown in FIG. 5, the part of the multilayersubstrate 100 below the dashed line 104 can be regarded as a first layerarrangement comprising a plurality of layers. The part of the multilayersubstrate 100 above the dashed line 104 can be regarded as a secondlayer arrangement. The first layer arrangement has a cutoutcorresponding to a lateral course of the waveguide 102 in a surfacethereof. A metallization is provided on the surface of this cutout. Thesecond layer arrangement has on an underside thereof a metallization,which together with the metallization on the surfaces of the cutoutforms the waveguide. The metallization on the second layer arrangementleaves open predetermined lateral regions 24, 26 of the cutout in thevertical direction, e.g. upward in FIG. 5. In the example shown, thepredetermined lateral regions are lateral ends of the cutout.Furthermore, the second layer arrangement has openings 28, 30 at thepredetermined lateral regions 24, 26, wherein surfaces of the openings28, 30 in the second layer arrangement are metallized and form anextension of the waveguide 102 through at least parts of the secondlayer arrangement. This extension can extend in a vertical direction,while the rest of the waveguide 102, e.g. in the first layerarrangement, extends in a lateral direction.

Coupling elements in the form of patch antennas 150, 152 are provided ina manner overlapping the openings 28, 30 in order to couple RF signalsinto the waveguide 102 and to couple the signals out of the waveguide.The patch antennas 150, 152 can be connected to a respective RF solderball 158, 159 of the LO master 110 and of the LO slave 112 by way of arespective line structure 154, 155 and a respective RF-suitable via 156,157. The line structure 154, 155 can comprise for example a microstripline and a matching structure for impedance matching. In examples, themicrostrip line itself can fulfill the function of impedance matching.

In the example of a circuit device as shown in FIG. 5, an RF signal isconducted into the interior of the multilayer substrate 100 by way ofthe RF solder ball 158 and the RF-suitable via 156. In the interior,impedance matching can be carried out by way of the line structure 154and the RF signal can be routed to the patch antenna 150 by way of amicrostrip line of the line structure 154. The patch antenna 150 emitsthe RF signal into the waveguide 102 integrated into the multilayersubstrate 100. The RF signal is received again on the part of the LOslave 112 by way of the further patch antenna 152. From the patchantenna 152, the RF signal can be routed to the RF solder ball 159 ofthe LO slave 112 by way of the line structure 155 and the RF-suitablevia 157.

The example shown in FIG. 5 may be advantageous to the effect that theMMIC circuits do not have to be integrated into the multilayersubstrate, but rather can be provided on a surface of the multilayersubstrate. It is thus possible to reuse customary heat dissipationconcepts since the MMIC circuits are not covered.

FIG. 6 shows one example of a circuit device in which the MMIC circuits110 and 112 are recessed into the multilayer substrate 100 and thewaveguide 102 is not integrated downward into the multilayer substrate,but rather is emplaced from above. The MMIC circuits 110, 112 arearranged in cutouts in a surface of the multilayer substrate. In theexample shown in FIG. 6, that part of the multilayer substrate 100 whichis arranged above the dashed line 104 can be regarded as a first layerarrangement, and that part of the multilayer substrate 100 which isarranged below the dashed line 104 can be regarded as a second layerarrangement. The waveguide is once again formed by correspondingmetallizations on surfaces of a cutout in the first layer arrangementand on the second layer arrangement. Once again vertical sections of thewaveguide extend through openings 28 and 30 in the second layerarrangement, the waveguide being open downward in this example. Onceagain patch antennas 150 and 152 are coupled to the openings in order tocouple corresponding RF signals into the waveguide and to couple themout of the latter. Since the MMIC circuits 110 and 112 are recessed intothe multilayer substrate 100, RF-suitable vias are not required in thisexample. Rather, the line structures 154, 155 are directly connected torespective solder balls 158, 159 of the assigned MMIC element 110, 112.The example shown in FIG. 6 may be advantageous to the effect thatcustomary layer constructions of a multilayer substrate can be reused.

FIG. 7 shows a further example of a circuit device in which the MMICelements 110 and 112 are recessed into the multilayer substrate 100 andthe waveguide 102 is integrated downward into the multilayer substrate.The MMIC elements are arranged in cutouts in a surface of the multilayersubstrate 100. In this example, once again the part of the multilayersubstrate below the dashed line 104 can be regarded as a first layerarrangement and the part above the line can be regarded as a secondlayer arrangement. The waveguide 102 can thus be formed in themultilayer substrate 100 in a manner similar to that in the case of theexample shown in FIG. 5. Since the MMIC elements 110 and 112 are onceagain recessed in the multilayer substrate, an RF-suitable via is notrequired and the respective patch antennas 150 and 152 can once again beconnected directly to a respective solder ball 158, 159 of therespective MMIC element 110 and 112 by way of a respective linestructure 154, 155. In order to prevent emission from the patch antennas150 and 152 upward, reflectors 170 and 172 can respectively be provided,which are arranged on sides of the patch antennas 150 and 152 facingaway from the waveguide 102. The reflectors 170 and 172 can be formedfor example by corresponding metallizations in that layer of themultilayer substrate 100 which is arranged above the patch antennas 150and 152. The reflectors 170 and 172 can thus be integrated into theprinted circuit board. Since, in the example shown in FIG. 7, thewaveguide extends from the patch antennas 150 and 152 downward into themultilayer substrate 100 and reflectors 170 and 172 are provided, theMMIC elements 110 and 112 need not be recessed into the multilayersubstrate 100 as far as in the example shown in FIG. 6.

A further example of a circuit device is shown in FIG. 8. In the exampleshown in FIG. 8, the MMIC elements 110 and 112 are integrated into themultilayer substrate. To put it more precisely, the MMIC elements 110and 112 are inserted in cutouts in the multilayer substrate. In thisexample, the multilayer substrate comprises a first part 100 a and asecond part 100 b. The MMIC elements are inserted in cutouts of thefirst part 100 a which are open upward. The second part 100 b is placedonto the first part 100 a. The waveguide 102 is formed in the secondpart 100 b, as described herein. In this case, that part of themultilayer substrate which is situated above the dashed line 104 can beregarded as a first layer arrangement, and that part of the multilayersubstrate 100 or of the second part 100 b of the multilayer substratewhich is situated below the dashed line 104 can be regarded as a secondlayer arrangement. Openings 28 and 30, which penetrate through thesecond layer arrangement completely or partly, depending on thestandpoint, are arranged in such a way that they are arranged oppositepatch antennas 180 and 182 integrated into the housing of the MMICelements 110 and 112.

In the example shown in FIG. 8, the first part 100 a and the second part100 b of the multilayer substrate can be produced separately from oneanother, and the second part 100 b, which comprises the waveguide 102,can be placed onto the first part 100 a. In this variant, the antennascan be situated in the housing, package, on the rear side of the MMICelements. In the case of such an arrangement, an RF transition from therespective MMIC element to the multilayer substrate is not necessary,with the result that fewer losses occur and more expedient printedcircuit boards can be used.

It is evident to those skilled in the art that other implementations arepossible besides the examples shown in FIGS. 5 to 8. Generally, examplesof the present disclosure provide a circuit device in which a waveguideis integrated into a multilayer substrate in order to transfer RFsignals between RF elements formed in or on the multilayer substrate. Inthis case, the RF elements can comprise RF circuits, such as, forexample, RF circuit chips, and/or antennas. In examples, the multilayersubstrate can comprise signal routing structures comprising vias andconductor tracks, wherein the circuit device comprises RF elements on orin the multilayer substrate, wherein at least one terminal of a first RFelement is coupled by way of the at least one waveguide to a terminal ofa second RF element for signal transfer between same. In examples, theRF elements can comprise a local oscillator circuit, at least onetransmitting/receiving circuit and at least one antenna, wherein the atleast one waveguide is configured to transfer an output signal of thelocal oscillator circuit to the transmitting/receiving circuit, and/orwherein the at least one waveguide or a further waveguide couples the atleast one transmitting/receiving circuit to the at least one antenna. Inthis case, the local oscillator circuit can be part of atransmitting/receiving circuit, such that two transmitting/receivingcircuits, with at least one of the transmitting/receiving circuitscomprising a local oscillator circuit, can be connected by way of thewaveguide.

In examples, the circuit arrangement is a radar circuit arrangement,wherein the RF elements comprise a plurality of transmitting/receivingcircuits, a plurality of receiving antennas, a plurality of transmittingantennas, and a local oscillator circuit, wherein a plurality ofcorresponding waveguides are provided, which couple the local oscillatorcircuit to each of the transmitting/receiving circuits and couple thetransmitting/receiving circuits to the plurality of receiving antennasand transmitting antennas. One example of such a circuit device is shownin FIG. 9.

Examples of the disclosure provide a radar system comprising amultilayer substrate, at least one waveguide formed in the multilayersubstrate, a first semiconductor radar transmitting/receiving circuitand a second semiconductor radar transmitting/receiving circuit, whereinthe first semiconductor radar transmitting/receiving circuit is coupledto the second semiconductor radar transmitting/receiving circuit by wayof the waveguide, or wherein the first semiconductor radartransmitting/receiving circuit and the second semiconductor radartransmitting/receiving circuit are coupled to a local oscillator circuitby way of a respective waveguide. One example of such a cascaded radarsystem is shown in FIG. 9, wherein a plurality of semiconductor radartransmitting/receiving circuits 62, 64, 66, 68 are coupled to a localoscillator circuit 60. In other examples, the LO master is notimplemented as a separate LO circuit, but rather is formed by a localoscillator in one of the transmitting/receiving circuits. One of thetransmitting/receiving circuits can thus act as LO master, whichforwards the local oscillator signal to one or more othertransmitting/receiving circuits.

In examples, the first and second semiconductor radartransmitting/receiving circuits are configured to generate frequencyramps using a local oscillator signal, wherein at least either the firstor the second semiconductor radar transmitting/receiving circuit isconfigured to receive the local oscillator signal by way of the at leastone waveguide. By way of example, the transmitting/receiving circuits 62to 68 shown in FIG. 9 can receive an LO signal by way of waveguides ofthe LO distribution network 70. All transmitting/receiving circuits,transceivers, can thus use the same radio-frequency LO signalphase-synchronously to down-convert received radar signals to thebaseband, for example.

In examples of the present disclosure, the waveguide or the waveguidesof the radar system is or are produced by methods as described herein.Examples of the radar system can thus be produced using individual orall features of methods as described herein for producing a waveguide ina multilayer substrate. In the same way, radar systems as describedherein can have some or all features of circuit devices as describedherein.

Examples of the present disclosure make it possible to transfer RFsignals in radar devices, for example automobile radar devices, with lowlosses and little crosstalk. Examples enable radar sensors having anincreased angular resolution since a larger number of channels can beintegrated in a multilayer substrate with longer RF feed lines onaccount of the lower signal losses and the lower crosstalk. As a result,examples of the present disclosure enable increased objectdifferentiability on account of the increased angular resolution.Examples thus enable a cascading of a plurality of radar MMICs eachcomprising a plurality of transmitting and receiving antennas.

Although some aspects of the present disclosure have been described asfeatures in association with a device, it is clear that such adescription can likewise be regarded as a description of correspondingmethod features, in particular production method features. Although someaspects have been described as features in association with a method, inparticular a production method, it is clear that such a description canalso be regarded as a description of corresponding features of a deviceor of the functionality of a device.

In the detailed description above, in some instances different featureshave been grouped together in examples in order to rationalize thedisclosure. This type of disclosure ought not to be interpreted as theintention that the claimed examples have more features than areexpressly indicated in each claim. Rather, as represented by thefollowing claims, the subject matter can reside in fewer than allfeatures of an individual example disclosed. Consequently, the claimsthat follow are hereby incorporated in the detailed description, whereineach claim can be representative of a dedicated separate example. Whileeach claim can be representative of a dedicated separate example, itshould be noted that although dependent claims refer back in the claimsto a specific combination with one or more other claims, other examplesalso comprise a combination of dependent claims with the subject matterof any other dependent claim or a combination of each feature with otherdependent or independent claims. Such combinations shall be encompassed,unless an explanation is given that a specific combination is notintended. Furthermore, the intention is for a combination of features ofa claim with any other independent claim also to be encompassed, even ifthis claim is not directly dependent on the independent claim.

The examples described above are merely illustrative for the principlesof the present disclosure. It should be understood that modificationsand variations of the arrangements and of the details described areobvious to those skilled in the art. Therefore, the intention is for thedisclosure to be limited only by the appended patent claims and not bythe specific details set out for the purpose of the description andexplanation of the examples.

1. A method for producing a waveguide in a multilayer substrate, themethod comprising: producing at least one cutout corresponding to alateral course of the waveguide in a surface of a first layerarrangement comprising one or a plurality of layers; producing ametallization on surfaces of the at least one cutout; applying a secondlayer arrangement comprising one or a plurality of layers on the firstlayer arrangement, wherein the second layer arrangement comprises, on asurface thereof, a metallization which, after the second layerarrangement has been applied on the first layer arrangement, is arrangedabove the at least one cutout and together with the metallization on thesurfaces of the at least one cutout forms walls of the waveguide.
 2. Themethod as claimed in claim 1, wherein the at least one cutout does notcompletely penetrate through the first layer arrangement in a verticaldirection with respect to a main surface of the first layer arrangement,or the at least one cutout completely penetrates through the first layerarrangement in a vertical direction with respect to a main surface ofthe first layer arrangement, wherein the method further comprisesapplying a third layer arrangement on the first layer arrangement,wherein the third layer arrangement comprises a metallization, andwherein the second layer arrangement and the third layer arrangement areapplied on two opposite surfaces of the first layer arrangement, whereinthe metallizations on the second layer arrangement and the third layerarrangement together with the metallization on the surfaces of the atleast one cutout form walls of the waveguide.
 3. The method as claimedin claim 1, wherein the metallization on the second layer arrangementdoes not cover regions of the at least one cutout at predeterminedlateral regions thereof or wherein the metallization on the second layerarrangement is removed at predetermined lateral regions of the at leastone cutout after the second layer arrangement has been applied.
 4. Themethod as claimed in claim 3, wherein the metallization on the surfacesof the at least one cutout and the metallization on the second layerarrangement extend continuously between the predetermined lateralregions.
 5. The method as claimed in claim 3, wherein the second layerarrangement has openings at the predetermined lateral regions of the atleast one cutout or wherein openings are produced in the second layerarrangement at the predetermined lateral regions of the at least onecutout.
 6. The method as claimed in claim 5, wherein surfaces of theopenings in the second layer arrangement have been or are metallized andthe openings form an extension of the waveguide through at least partsof the second layer arrangement.
 7. The method as claimed in claim 3,wherein provision is made of coupling elements to couple signals intoand out of the waveguide at the predetermined lateral regions at whichthe metallization on the second layer arrangement does not cover the atleast one cutout.
 8. The method as claimed in claim 7, wherein at leastone coupling of the coupling elements is formed by an antenna, whereinthe antenna is formed in or on a housing of a radio frequency circuitchip fitted in or on the multilayer substrate, or wherein the antenna isfitted on the multilayer substrate.
 9. The method as claimed in claim 7,wherein reflectors are provided on a side of the coupling elementsfacing away from the first layer arrangement.
 10. The method as claimedin claim 1, wherein the at least one cutout is formed by milling or by alaser treatment in the first layer arrangement.
 11. The method asclaimed in claim 1, wherein the first layer arrangement comprises aplurality of layers of the multilayer substrate, in which signal routingstructures comprising vias and conductor tracks are formed.
 12. Themethod as claimed in claim 1, wherein the second layer arrangementcomprises a plurality of layers of the multilayer substrate, in whichsignal routing structures comprising vias and conductor tracks areformed, or wherein the first layer arrangement and the second layerarrangement are fitted on a plurality of layers of the multilayersubstrate, in which signal routing structures comprising vias andconductor tracks are formed.
 13. A method for producing a circuitcomprising a multilayer substrate, the method comprising: producing themultilayer substrate comprising a plurality of layers, in which signalrouting structures comprising vias and conductor tracks are formed, andthe multilayer substrate comprising radio frequency (RF) elements on orin the multilayer substrate, wherein at least one waveguide is formed inthe multilayer substrate by a method as claimed in claim 1, and whereinat least one terminal of a first RF element, of the RF elements, iscoupled by way of the at least one waveguide to a terminal of a secondRF element, of the RF elements, for signal transfer between the first RFelement and the second RF element.
 14. The method as claimed in claim13, wherein the RF elements comprise a local oscillator circuit, atleast one transmitting/receiving circuit and at least one antenna,wherein forming the at least one waveguide comprises forming a waveguidethat couples the local oscillator circuit to the at least onetransmitting/receiving circuit, and/or forming a waveguide that couplesthe at least one transmitting/receiving circuit to the at least oneantenna.
 15. The method as claimed in claim 1, wherein the circuit is aradar circuit, wherein the RF elements comprise a plurality oftransmitting/receiving circuits, a plurality of receiving antennas, aplurality of transmitting antennas, and a local oscillator circuit,wherein forming the at least one waveguide comprises forming a pluralityof waveguides in order to couple the local oscillator circuit to each ofthe plurality of transmitting/receiving circuits, and to couple theplurality of transmitting/receiving circuits to the plurality ofreceiving antennas and the plurality of transmitting antennas.
 16. Acircuit device, comprising: a multilayer substrate; at least onewaveguide integrated into the multilayer substrate; a first layerarrangement comprising one or a plurality of layers, wherein the firstlayer arrangement comprises a cutout corresponding to a lateral courseof the at least one waveguide in a surface thereof; a metallization onsurfaces of the cutout; a second layer arrangement, which comprises oneor a plurality of layers and is applied on a surface of the first layerarrangement, wherein a metallization on the second layer arrangement isarranged above the cutout and together with the metallization on thesurfaces of the cutout forms the at least one waveguide, wherein themetallization on the second layer arrangement leaves open predeterminedlateral regions of the cutout in a vertical direction; and couplingelements for to couple signals into and out of the at least onewaveguide at the predetermined lateral regions of the cutout that areleft open in the vertical direction.
 17. The circuit device as claimedin claim 16, wherein the second layer arrangement has openings at thepredetermined lateral regions of the cutout, wherein surfaces of theopenings in the second layer arrangement are metallized and form anextension of the at least one waveguide through at least parts of thesecond layer arrangement.
 18. The circuit device as claimed in claim 16,wherein at least one of the coupling elements is formed by an antenna,wherein the antenna is formed in or on a housing of a radio frequencycircuit chip fitted in or on the multilayer substrate, or the antenna isfitted on the multilayer substrate.
 19. The circuit device as claimed inclaim 16, wherein reflectors are provided on a side of the couplingelements facing away from the first layer arrangement.
 20. The circuitdevice as claimed in claim 16, wherein the multilayer substratecomprises signal routing structures comprising vias and conductortracks, and wherein the circuit device comprises radio frequency (RF)elements on or in the multilayer substrate, wherein at least oneterminal of a first RF element, of the RF elements, is coupled by way ofthe at least one waveguide to a terminal of a second RF element of theRF elements, for signal transfer between the first RF element and thesecond RF element.
 21. The circuit device as claimed in claim 20,wherein the RF elements comprise a local oscillator circuit, at leastone transmitting/receiving circuit and at least one antenna, wherein theat least one waveguide is configured to transfer an output signal of thelocal oscillator circuit to the transmitting/receiving circuit, and/orwherein the at least one waveguide or a further waveguide couples the atleast one transmitting/receiving circuit to the at least one antenna.22. The circuit device as claimed in claim 20, which is a radar circuitarrangement, wherein the RF elements comprise a plurality oftransmitting/receiving circuits, a plurality of receiving antennas, aplurality of transmitting antennas, and a local oscillator circuit,wherein the at least one waveguide includes a plurality of waveguides,which couple the local oscillator circuit to each of the plurality oftransmitting/receiving circuits and couple the plurality oftransmitting/receiving circuits to the plurality of receiving antennasand the plurality of transmitting antennas.
 23. A radar system,comprising: at least one waveguide formed in a multilayer substrate; anda first semiconductor radar transmitting/receiving circuit and a secondsemiconductor radar transmitting/receiving circuit, wherein the firstsemiconductor radar transmitting/receiving circuit is coupled to thesecond semiconductor radar transmitting/receiving circuit by way of theat least one waveguide, or wherein the first semiconductor radartransmitting/receiving circuit and the second semiconductor radartransmitting/receiving circuit are coupled to a local oscillator circuitby way of a respective one of a first waveguide, of the at least onewaveguide, and a second waveguide of the least one waveguide.
 24. Theradar system as claimed in claim 23, wherein the first semiconductorradar transmitting/receiving circuit and the second semiconductor radartransmitting/receiving circuit are configured to generate frequencyramps using a local oscillator signal, wherein the first semiconductorradar transmitting/receiving circuit or the second semiconductor radartransmitting/receiving circuit is configured to receive the localoscillator signal by way of the at least one waveguide.
 25. The radarsystem as claimed in claim 23, wherein the multilayer substrate is afirst multilayer substrate and the at least one waveguide is at leastone first waveguide; and wherein the radar system further comprises: asecond multilayer substrate; at least one second waveguide integratedinto the second multilayer substrate; a first layer arrangementcomprising one or a plurality of layers, wherein the first layerarrangement comprises a cutout corresponding to a lateral course of theat least one second waveguide in a surface thereof; a metallization onsurfaces of the cutout; a second layer arrangement, which comprises oneor a plurality of layers and is applied on a surface of the first layerarrangement, wherein a metallization on the second layer arrangement isarranged above the cutout and together with the metallization on thesurfaces of the cutout forms the at least one second waveguide, whereinthe metallization on the second layer arrangement leaves open regions ofthe cutout at lateral ends thereof in a vertical direction; and couplingelements for to couple signals into and out of the at least one secondwaveguide at the regions of the cutout that are left open in thevertical direction.